The Raccoon River makes a lazy entrance into Des Moines, completing its journey from northwest Iowa in a series of graceful switchbacks through an urban park, its olive surface shaded by locust trees and towering cottonwoods. At the edge of downtown it turns north and, on the southern bank, passes a squat concrete culvert: the main intake for the Des Moines Water Works, which supplies drinking water to the city. The scene has the pastoral calm of an English landscape painting and gives the impression of a river scarcely touched by progress or tainted by the twentieth century.
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But sometime in the 1980s, biochemists working for the waterworks began to detect something wrong with the river. At a chemistry lab inside a stately brick building not far from the intake culvert, they tested river water samples and found rising levels of nitrate, the nutrient that forms as part of the nitrogen cycle. The chemical conversion, which happens naturally in soil and water, changes the harmless element N2 into a compound that, in high concentrations, has been linked to premature births and several cancers.
In a state where one in six jobs depends on agriculture…no one had ever tried to make farmers pay for pollution.
They continued to monitor the river, and in 1989 found that its nitrate levels had shot above ten milligrams per liter, the federal government’s threshold for safe drinking water. The Iowa Department of Health and Human Services ordered Des Moines to treat the water. The utility’s trustees, a board of five appointed by the mayor, went to ratepayers, raised $4.1 million, and in 1992 christened a state-of-the-art facility consisting of eight massive steel tanks that could purify ten million gallons of water a day and would kick in whenever the river’s nitrate content reached unsafe levels. On the day it began operation, it was the largest nitrate-removal facility in the world.
But nitrate levels in the Raccoon River kept on rising.
In 2013 peak nitrate loads in the lab’s samples of river water hit twenty-four milligrams per liter, more than twice the federal safety standard. Forced to reduce their draw from the Raccoon River that summer, the waterworks trustees issued a plea to the people of Des Moines to conserve water and cut back on lawn sprinkling. The nitrate-removal plant operated for a record seventy-four days that fall.
By this time, the trustees had good reason to be alarmed. The federal government had begun regulating nitrate in 1997 after a series of public health studies linked it to several medical conditions, including a phenomenon known as “blue baby syndrome,” in which an infant’s blood loses its ability to carry sufficient oxygen to the body’s organs. A bad case can cause a baby’s skin to turn blue; a severe case can cause cell damage and even death. After federal regulations took effect, cases of blue baby syndrome became quite rare. But the scare caused medical researchers to probe for other health threats from nitrate. And before long they had found several. A study of Missouri infants born between 2004 and 2008 found an increased risk of limb abnormalities, heart defects, and neural tube defects such as spina bifida in babies whose mothers were exposed to drinking water with nitrate levels at half the federal safety ceiling. Subsequent research from a project known as the Iowa Women’s Health Study found higher risk of bladder cancer and thyroid disease in women with more than four years of exposure to drinking water with nitrate levels above five milligrams per liter. In 2019 researchers writing in the journal Environmental Research estimated that across the country, elevated nitrate levels in drinking water caused more than 2,900 low-birthweight babies annually, 1,725 premature births, and roughly 6,500 excess cancers of the bladder, ovaries, colon, and thyroid. Together, these cost the U.S. healthcare system at least $250 million a year. But even collectively, the research found only correlations that might implicate nitrate—not the hard proof of causation required to trigger the difficult and controversial process of tightening federal health regulations.
The waterworks had a backup water source, the Des Moines River. But it faced an even more frightening problem: heavy blooms of blue-green algae in a reservoir fed by the river, caused by warm weather and excess nitrate from fertilizer. The algae grows in slow-moving water, and produces a primitive microbe called cyanobacteria, which is highly toxic to humans and animals. Unlike nitrate buildup, which can take weeks or months, cyanotoxins can appear in lakes or slow-moving streams overnight and make the water instantly unsafe to drink. In 2014, on Ohio’s Maumee River near Toledo, a combination of fertilizer runoff and unusual weather sparked a massive algae bloom that turned the water a putrid green and sent cyanotoxin levels to twice the maximum allowed by federal law. The city ordered an emergency shutdown of its waterworks. Stores sold out of bottled water within hours and the governor sent in the National Guard to deliver water and ready-to-eat meals to homes across the city.
Facing these threats, the waterworks trustees were left with two choices: massively increase their spending to treat Raccoon River water or expose the people of Des Moines to grim health risks.
Des Moines’s predicament was not unusual. The twin triumphs of synthetic nitrogen and highly efficient tile drainage didn’t merely foul the Mississippi River and the Gulf of Mexico, they sent large volumes of nitrate into the drinking water sources of the upper Midwest. In Iowa alone, some sixty other towns and cities had to treat their drinking water for elevated nitrates; across the Midwest thousands of private wells, mostly unregulated by state health authorities, were contaminated too. In state after state, thousands of people were discovering that their tap water might be unsafe to drink.
What set Des Moines apart was a public servant named Bill Stowe, the general manager of the city’s waterworks and a guy who wasn’t afraid to challenge the status quo. Stowe was alarmed by the nitrate levels and he was pretty sure he knew where it was coming from: the heavily fertilized farm fields around the river’s source in northwestern Iowa and the drainage tiles that carried excess nitrogen off the fields and into local waterways.
In the spring of 2014, Stowe dispatched a team of employees to test his hunch. They drove 150 miles north and west to the upper reaches of the Raccoon River, amid the network of drainage ditches and straightened streams that crisscross the farms of the Des Moines Lobe. Parking on county roads that provided public access to private land, they held their collection bottles beneath the drain pipes that poked out of fields alongside creeks and ditches. Stopping at twenty-seven sites in three counties, they filled scores of sample flasks. Back at the lab, they found what Stowe had expected: Dozens of the water samples showed extremely high levels of nitrate—many exceeding ten milligrams and some exceeding twenty.
It was dry that year and Raccoon River ran unusually low, concentrating its contaminants as the summer weeks rolled by. The waterworks’s nitrate-removal plant, which had never been used for more than a few months annually, ran for 177 days that year, costing ratepayers more than $2 million. Stowe warned his trustees that if the nitrate didn’t subside, it would soon overwhelm the plant. An upgrade could cost as much as $80 million and force a double-digit rate increase for the citizens of Des Moines.
The city of Des Moines, Iowa, gets its drinking water from the intensively farmed Raccoon River watershed, where the vast majority of land is planted in corn and soybeans. The Des Moines Water Works unsuccessfully sued three county drainage authorities in the upper reaches of the watershed for failing to stop farm chemicals from polluting the city’s water. Graphic by Alexander Hage.
Art Cullen, editor of the Storm Lake Times Pilot in west-central Iowa, remembers that year well. Cullen grew up not far from Raccoon River, near the lovely lake that gave his town its name, and he treasured the little country sloughs and prairie potholes that throbbed with wildlife. But he had also seen pristine small lakes turn into muddy swamps because of soil erosion, and he was known for fearless editorials on agriculture and water pollution—work that eventually earned him a Pulitzer Prize. That year Cullen appeared with Stowe at a panel discussion organized by the Iowa Environmental Council. When their presentation ended and the crowd was thinning out, Stowe leaned over to Cullen and said, “I’m going to sue your county.” Cullen knew that Stowe was giving him a big story. He remembers thinking, This guy has no fear.
The waterworks’s lawsuit, announced in January 2015, had a simple premise: People who pollute a river should pay to clean it up. It asked the court to order three counties along the upper reaches of the Raccoon River—Calhoun, Sac, and Buena Vista—to reduce nitrate levels running into the river through the farm drainage ditches they supervised.
A win for the Des Moines Water Works could set a legal precedent that would change environmental law nationally.
Stowe and his trustees conceived the legal strategy carefully. They knew that suing individual landowners was a fool’s errand. Farmers command enormous public sympathy in Iowa and, in any case, no one farmer could reengineer the hydrology of the entire Des Moines Lobe. Instead, the lawsuit targeted that obscure but powerful unit of local government: the drainage district. These descendants of Alonzo Thornton’s vision had supervised the epic replumbing of Iowa farmland in the nineteenth century and continued to wield substantial power into the twentieth. They could commission dredging projects costing hundreds of thousands of dollars, levy assessments on any landowner who benefited from drainage, and even use eminent domain to acquire land they desired. They were so valuable to Iowa agriculture that their powers were enumerated in state statutes and protected by a special provision of the state constitution. Taken together, the state’s three thousand drainage district boards controlled the water that fell on more than a quarter of Iowa’s farmland. They replaced nature’s tools for managing excess water—sloughs, bogs, and meandering streams—with local officials whose mission was to dry out the land as fast as possible.
If they had that much power to move water, Stowe reasoned, they had the power and the responsibility to clean it up.
The lawsuit struck Iowa like a thunderclap. In a state where one in six jobs depends on agriculture, where almost everyone grew up in the country or knows someone who did, no one had ever tried to make farmers pay for pollution. No one had even considered it. Farmers were widely regarded as stewards of the land and pillars of the community; their property taxes funded rural schools, their commerce supported small-town retailers. They fed the world and earned billions of dollars for Iowa’s economy in the process. The lawsuit not only challenged one of Iowa’s cherished myths—the farmer as conservationist—it indicted one of the state’s proudest historical achievements, the vast system of drainage ditches that had converted the hated mosquito bogs of the Des Moines Lobe into priceless farmland.
It also deepened the emerging cultural rift between Iowa’s urban and rural communities. In a state known for corn and hogs, Des Moines is the urban heart, a metro area of 500,000 people and a regional center of banking and insurance. It has a clean and bustling downtown, a historic warehouse district with brew pubs and ethnic restaurants, and a well-educated and civic-minded population—many who are sympathetic to environmental causes. But to many rural Iowans, it was “the big city,” a place of traffic congestion, liberal ideas, and arrogant urbanites.
Almost overnight the lawsuit attracted national attention in the conservation and public health communities. Which was no surprise. Across the Midwest more than three thousand streams and river segments had been declared “impaired” under federal law—unsafe for drinking, swimming, or fishing—mostly because of farm chemicals. Thousands of private wells across the upper Midwest had tested positive for excess nitrates. Along the Missouri River near St. Louis, outbreaks of poisonous blue-green algae, often caused by excess phosphorus and nitrogen, had forced several communities to close parks and beaches. In the Chesapeake Bay, runoff of nutrients and sediment from farms and suburban lawns was snuffing out aquatic life. A win for the Des Moines Water Works could set a legal precedent that would change environmental law nationally.
The lawsuit also underscored a crucial but little-known feature of federal environmental regulation. Agriculture is largely exempt from the nation’s core water pollution law, the Clean Water Act. The law, passed in the early 1970s, focused on large “point source” polluters such as factories and sewage treatment plants, which are easy to identify and simple to regulate. The nation’s three million farms—small, widely dispersed, and hard to regulate—mostly got a pass.
The Des Moines lawsuit promised to change that.
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Excerpted from Sea of Grass: The Conquest, Ruin, and Redemption of Nature on the American Prairie by Dave Hage and Josephine Marcotty. Copyright © 2025 by Dave Hage and Josephine Marcotty. Used by permission of Random House, an imprint and division of Penguin Random House LLC, New York. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.